1. Field of the Invention
The present invention relates to a robot control apparatus for controlling a robot using an imaging device, and more particularly to a robot control apparatus for controlling a robot using an imaging device in order to determine a relative position of a workpiece to the robot and correct a teaching point position of an operation program for the robot based on the determined relative positions.
2. Description of the Related Art
In the field of an industrial robot, an imaging device, such as a camera has been widely used as an eye for a robot. In the case where an imaging device is used for an industrial robot, it is common for the imaging device to be connected to an image processing unit separately provided from or integral with a robot control apparatus and the image processing device and an image display unit for displaying the image thereon are arranged integrally with or in the vicinity of the robot control apparatus. In a factory, it is common to surround the operating range of the robot with a protective fence or the like for the safety of an operator and to arrange the robot control apparatus and the image processing unit outside the protective fence at a sufficient distance from the robot.
As described above, where the image processing unit and the image display unit are installed is often far from the robot, and this poses a problem in that it is difficult to check an image picked up by the imaging device during a robot teaching operation or an adjustment operation of the image processing unit or the imaging device. In order to solve this problem, Japanese Unexamined Patent Publication No. 2000-135689, Japanese Unexamined Patent Publication No. 2001-191285 and Japanese Unexamined Patent Publication No. 2001-121458, for example, propose a portable teaching pendant having an image display and used for the operation of the robot or the image processing unit. The use of this teaching pendant makes it possible for the operator to display an image picked up by the imaging device on the teaching pendant. Therefore, an operator, manually operating the robot, can check the image on the teaching pendant during the robot teaching operation or the adjustment operation of the imaging device or the image processing unit.
The imaging device and the image processing unit (hereinafter collectively referred to as a visual sensor) of the industrial robot, as described above, function as an eye of the robot for doing a job and is continuously used while the robot is used. Therefore, once installed, the visual sensor is basically not removed from the robot.
However, in recent years, the visual sensor has been temporarily used only when installing the robot system. Japanese Unexamined Patent Publication No. 2005-149299, for example, discloses a teaching position correcting device in which in order to facilitate an operation for correcting teaching points in a robot operation problem at the time of relocation of a robot system, displacement of the relative positions between the installation place of the robot and the workpiece place, which may occur after the relocation of the robot system, is measured by a camera temporarily mounted on the robot to correct positions of teaching points in the robot operation program. The teaching position correcting device 100 disclosed in Japanese Unexamined Patent Publication No. 2005-149299, as shown in FIG. 5, includes an image processing unit 104 connected to a robot control apparatus 102, and a CCD camera 112 connected to the image processing unit 104 by a camera connecting cable 110. An image is picked up by a CCD camera 112 mounted on a working tool 114 of the robot 106 while an operator is operating a teaching pendant 108 connected to the robot control apparatus 102. The image thus picked up is processed by the image processing unit 104, so that three-dimensional positions of three reference marks 120 provided on a holding unit 118 for holding a workpiece 116 are measured to calculate a change in the position of the holding unit 118 relative to the robot 106 based on the positions of the reference marks 120 measured before and after relocation, and the positions of the teaching points defined in the robot operation program are corrected by the calculated change amount.
The image processing unit 104 used in the teaching position correcting device 100 disclosed in Japanese Unexamined Patent Publication No. 2005-149299 is similar to the image processing units disclosed in Japanese Unexamined Patent Publication No. 2000-135689, Japanese Unexamined Patent Publication No. 2001-191285 and Japanese Unexamined Patent Publication No. 2001-121458 and is installed in the vicinity of the robot control apparatus. Further, the CCD camera 112 is connected to the image processing unit 104.
On the other hand, the visual sensor constituted by the CCD camera 112 and the image processing unit 104, as disclosed in Japanese Unexamined Patent Publication No. 2005-149299, unlike a conventional visual sensor of the industrial robot, is not fixed to the robot 106, but used temporarily only to measure the positions of the reference marks 120 at the time of relocation, and one CCD camera 112 is generally used for a plurality of robots 106. Therefore, mounting and demounting the CCD camera 112 from the robot 106 and the robot control apparatus 102 is frequently carried out.
However, in starting a job on a robot 106 after finishing a job on another robot 106, the operator needs to move between the robot 106 and the robot control apparatus 102 installed at a distance from the robot 106 in order to reconnect the CCD camera 112 with the image processing unit 104 or the robot control apparatus 102. Especially on an actual production line, the robot 106 is surrounded by a protective fence for the safety of the operator, and the robot control apparatus 102 and the image processing unit 104 are arranged outside the protective fence. Therefore, the robot 106 and the robot control apparatus 102 are generally far from each other. Also, in some cases, the robot control apparatus 102 and the robot 106 are installed on different floors in a factory layout. Therefore, movement between the robot 106 and the robot control apparatus 102 imposes a heavy burden on an operator.